Leads having electrodes implanted in or about the heart have been used to reverse life-threatening arrhythmia or to stimulate contraction of the heart. For example, electrical energy is applied to the heart via an electrode to return the heart to normal rhythm. Leads are usually positioned on or in the ventricle or the atrium and the lead terminals are attached to a pacemaker or defibrillator which is implanted subcutaneously.
An issue concerning, for example, pacemaker leads is the increase in stimulation threshold, both acute and chronic, caused by the interaction between the electrode and body tissue at the point of implant. Approaches to reducing the threshold include silicone rubber based drug collars or plugs containing dexamethasone. However, in both cases, the lead design needs to accommodate the physical size of the plug or collar matrix. Also, dexamethasone is not very potent. Hence, high dosing is generally required. Moreover, these devices fail to address many of the physiological processes involved in the healing response upon lead implantation. Thus, there is a need for leads and/or electrodes that are constructed to more fully address the healing process so as to maintain optimal acute and chronic thresholds. In particular, there is a need for improved electrode performance.